The observable field is defined as the portion of the incident field that can contribute to the power received by an antenna. Recently, the observable field was estimated for a plane wave incidence. Here, the procedure is extended to a general incident field expressed as a superposition of homogeneous plane waves. The observable field concept provides a methodology to evaluate the maximum power that could be received by an ideal terminal antenna. In particular, it emerges that to maximize the received power, the pattern in transmission of the antenna should be synthesized to reproduce the angular pattern of the observable field. This is specifically relevant in cases of non-line of sight (NLOS) at high frequencies, where the power received can drop by orders of magnitude. As a case study, we consider a communication scenario which involves a base station and distributed receivers embedded in a complex scattering environment.